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Article

1,3-Butadiene Production Using Ash-Based Catalyst

by
Adama A. Bojang
and
Ho Shing Wu
*
Department of Chemical Engineering and Materials Science, Yuan Ze University, 135 Yuan Tung Road Chung Li, Taoyuan 32003, Taiwan
*
Author to whom correspondence should be addressed.
Catalysts 2023, 13(2), 258; https://doi.org/10.3390/catal13020258
Submission received: 14 November 2022 / Revised: 25 December 2022 / Accepted: 17 January 2023 / Published: 22 January 2023
(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)
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Abstract

:
The production of 1,3-butadiene from ethanol was carried out using ash as a catalyst in combination with Zr and Mg. The catalytic experiments were carried out at 350–400 °C with a different weight hourly space velocity (WHSV). The catalysts that were used were combined as follows: Ash, Ash:MgO (weight ratio 1:1), Ash:MgO (1:2), Ash:MgO (1:3), and Ash: MgO/ZrO2 (1:1:1). The characterization of the catalyst was carried out using BET, SEM, XRD, TGA, and XPS, respectively. The yield of 1,3-butadiene using bare ash was 65% at 400 °C and 2.5 h−1 of WHSV. Using the Ash:MgO (1:2) catalyst led to an ethanol conversion rate of 79 % at 350 °C; the yield and selectivity of 1,3-butadiene were 48% and 87.8 %, respectively. Using the Ash:MgO(1:3) catalyst led to a 1,3-butadiene yield of 25% and a selectivity of 82% at 350 °C. The Ash:MgO(1:2) catalyst had a 1,3-butadiene yield of 50% and selectivity of 83%, and the Ash:MgO(1:1) had a 1,3-butadiene yield of 30% and selectivity of 80%, while the Ash:MgO/ZrO2 (1:1:1) catalyst had a 1,3-butadiene yield of 50% and selectivity of 90.8% at 2.5 h−1 of WHSV.

1. Introduction

This study investigated the production of 1,3-butadiene from ethanol using ash in combination with ZrO2 and MgO. 1,3-Butadiene production from ethanol is of interest to countries that are poor in fossils but rich in biomass, such as sugar cane and cereals. In addition, there is an increased interest in fuel production from biomass due to its wide availability and carbon neutrality. 1,3-Butadiene is very important in the manufacturing of isomers in rubber industries. It can also produce organic chemicals in synthetic chemical reactions such as the Diels–Alder reaction. Since it belongs to the lower hydrocarbon group, its production is mostly from condensation reactions in the form of cracking. Since the 1,3-butadiene vintage hinges principally on the type of biomass or reactant of the condensation cracker, butadiene fabrication is vulnerable to issues in terms of unpredictability or styles in the gasoline business and in the evolving routine of gas, which might lead to butadiene deficiencies. The insufficiency of greenhouse gas-emitting fuel reserves is another long-term issue with the present hydrocarbon production methodology regarding its profitability and environmental properties [1,2,3].
Advanced technologies in ethanol production from biomass, combined with state subsidies and directives, have significantly made gains in terms of the productivity and affordability of bioethanol. An excess of bioethanol is expected due to its partial use as a fuel for combustion engines. For this reason, it is thought that ethanol could be an excellent molecule for the amalgamation of this value-added molecule. Angelici et al. recently outlined the conditions under which the industrial use of butadiene from bioethanol would reduce greenhouse gas emissions; the strategy is thought to use environmentally friendly ethanol sources [4]. Alternative case studies by Bhattacharyya et al. and Boronat et al. outlined that the conversion of ethanol and acetaldehyde into butadiene would be profitable under certain conditions; butadiene production in the Gulf Coast of the United States can be expected to be highly profitable as long as ethanol remains below $2.5/gallon [5,6]. In combination with MgO and ZrO2, Ash is required for the catalytic reaction of ethanol to 1,3-butadiene in a single fixed-bed reactor system. Ash contains trace elements such as Na, Ca, and Zn, which could serve as dopants. The support base was provided by the ash, which contains the silica. The dopant metals, such as Na and Zn, help in the dehydrogenation reaction of ethanol to relative products such as acetaldehyde, and Zr helps in or supports the catalyzation of aldol condensation to produce 1,3-butadiene. Some papers demonstrated that the adequate loading of MgO on ZrO2 could aid in a two-stage process of producing 1,3-butadiene from ethanol dehydration [1,7,8,9,10]. To avoid the low yield and productivity of 1,3-butadiene from ethanol, ash, Mg, and Zr, catalysts are used in a fixed bed or dual fixed bed reactor, as the catalyst had different metal constituents and would provide enough support for different metal-supported catalysts. An ash-combined catalyst consists of many or abundant metals such as Zr and Na that are well dispersed on the silica surface material. It provides good morphology for both the nanopores and mesocullar [11].
Aldol condensation generally produces 1,3-butadiene with appropriate acetaldehyde under homogeneous or heterogeneous conditions. The catalysts used in this work are Ash, MgO, and ZrO2 in different weight ratios. This catalyst possesses some Lewis acidic and basic characteristics, which can facilitate the production of 1,3-butadiene. Ash contains transitional metal-based mesoporous silicates, aluminophosphate, and mixed oxides, which are essential in various industrial production strategies of 1,3-butadiene and aid in transforming intermediate reactions [12,13,14].
Recently, the use of ZrO2 was extensively investigated for the dehydration of OH-functional groups and the dehydrogenation of alkyl compounds. Additionally, some solvent-free organic syntheses have been considered worldwide for the management of chemical waste. Thus, ash as a catalyst is cheap and safe to use in any environment [10,15,16]. Ash, as a catalyst combined with Mg and Zr, has many functional purposes that can balance the active sites for a good conversion of ethanol to butadiene. Evidence has shown that the combination of Lewis-acidic metallic oxides and dehydrogenation promoters can become suitable active catalysts [17]. Due to the complexity of the reaction conditions and the steps involved in ethanol’s catalytic conversion to butadiene, a multifunctional catalyst is needed to carry out the multi-step reaction mechanisms. These multi-purpose catalysts are driven by different elemental materials, which serve as promoters of the active sites for essential chemical reactions. Previous experimentation has shown the importance and specifics of the active sites in chemical catalytic experimentation, which demonstrates the acidic and basic sites and the redox reactivity properties [6,18,19]. The dehydrogenation of ethanol to acetaldehyde is typically carried out by the redox and primary site of the catalyst, and the acidic site favors the condensation and dehydration of ethanol to butadiene and ethylene [20,21,22]. Due to the convolution of the reaction, a balance between these properties must be achieved for excellent productivity. The quantity of diverse and active sites needs to be in suitable proportions to avoid the occurrence of undesired side reactions, such as the dehydration of ethanol; conversely, the similarity of the active sites on dissimilar catalytic systems remains an open question. For example, as stated by Chae et al. and summarized by Da Ros et al., Han et al., and Janssens et al., a vital topic in the design of the best catalysts is the similarity of the optimal catalytic purposes (acid/base/redox), the structure-catalytic association and the balance between them [20,23,24,25]. This study’s novelty used ash as an effective catalyst to produce 1,3-butadiene. Hence, ash is more cost-effective compared to other commercial catalysts. Additionally, its combination with Mg and Zr provides good reactivity and stability for the catalysts.

2. Results and Discussion

2.1. Characterization of Catalyst Using XRD

Figure 1 shows the XRD diffraction pattern of ash particles in combination with MgO at different proportions, i.e., (1:1), (1:2), and (1:3) and Ash-MgO/ZrO2 (1:1:1). The pattern of the Mg–oxalate complex and MgO particle was annealed at 700 °C for 8 h. The Mg–oxalate complex was formed in the calcination process of the MgO catalyst. The X-ray results show that previous studies highlighted the same phenomenon [26]. Generally, the XRD diffraction pattern of the Ash-MgO catalyst shows a strong and sharp diffraction peak at 2θ angles of 28.3°, 32.8°, and 39.5°, which correspond to the (111), (200), and (220) planes, respectively. In contrast, Mg(OH)2 diffraction peaks are located at 62.0° and 78.0°. As reported by other authors, these results revealed an essential feature of MgO [26,27,28]. Figure 1 shows the XRD pattern of ash, which contains calcite, quartz, and tridymite (SiO2) as major phases. After calcination at 600 °C, Na2O, CaO, and Al2O3 appeared as phases. The CaO obtained resulted from the decomposition of calcite, which seems to be amorphous, although it could be that some sort of crystallization process occurs as the calcination temperature reaches 550 °C. However, the peak at 63.8° could be identified as Al2O3, which resulted from the oxidation of alumina at 500 °C when ZrO2 was added to the mixture of Ash and MgO [29]. The ZrO2 peak was not as crystalline as pure ZrO2 (Figure 1). Thus, the peak appears to be broad, and a Si–Mg–Zr bond was formed, which suppressed the formation of the ZrO2 monoclinic as opposed to the more tetragonal ZrO2 [29]. MgO and SiO2 appear more distinct when ash is calcined with MgO at 600 °C (Figure 1). Figure S1 in the Supplementary Materials shows the XRD patterns for ash, MgO, and with different combination.
Ash + MgO (1:1) and (1:2) have a mixture of both a greater degree of crystallinity and amorphousness, while (1:3) has a higher intensity of crystal. Ash + MgO/ZrO2 (1:1:1) also displayed some crystallinity patterns.

2.2. Characterization of Catalyst Using XPS

The characterization of the catalysts of Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 was investigated by performing an XPS analysis. The XPS analysis revealed the appearance of magnesium in the outermost layers of the catalyst. The XPS analysis identified magnesium, carbon, oxygen, zirconium, and silicon (Mg 1s, C 1s, O 1s, Zr 3d, and Si 2p), as shown in Figure 2. Table 1 lists the percentage of oxygen, carbon, and magnesium for the catalyst Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2, which were 60.8%, 7.3%, and 1.0% for Ash:MgO (1:1), 58.7%, 9.9% and 3.8% for Ash:MgO (1:2), 62.6%, 5.8% and 4.4% for Ash: MgO (1:3), and 20.2%, and 44.4% and 14.0% for Ash:MgO/ZrO2, respectively. The level of Si decreased from 28.7% to 25.3% as the weight ratio of MgO increased from 1:1 to 1:2. When the ratio of Mg increased from 1:2 to 1:3, the level of Si also increased to 1.0%.
We compared the spectra line of Mg 1s and Si 2p between 150 and 200 eV. The different binding energies are associated with each species for O 1s. The binding energies are from 532 to 538 eV. The intensity of the O 1s peak varies in different catalyst combinations. As for Ash:MgO (1:1), the O 1s peak was 35000 au at 534 eV. For 1:2, the O 1s peak was 21,000 au at 530 eV. For 1:3, the O 1s peak was 20,000 au at 535 eV, and for Ash:MgO/ZrO2 (1:1:1), the O 1s peak was 33,000 au at 535 eV.
The shift in binding energies of O1s in different combinations of Ash and MgO can be explained as follows: for Ash:MgO (1:1), the chemical shift of the binding energy of O1s occurs at 535 eV with an intensity of 35,000 a.u; for Ash:MgO (1:2), the binding energy for O1s occurs at 530 eV and at an intensity of 21,000 a.u; Ash:MgO (1:3) has a chemical shift of O1s at 533 eV at an intensity of 20,000 a.u; and Ash:MgO/ZrO2 has a chemical shift of O1s at 534 eV and intensity of 32,000 a.u. The chemical shift of O1s could be due to the presence of the valance air of oxygen in the reaction environment in each sample, but at different amounts. In some reaction conditions, the valance pair could attract further reactions, while in some cases, it could be suppressed and become less reactive [30].

2.3. BET Profiles of the Catalyst

An ash and MgO combination was selected, as ash provides the silica content, which can provide the silica support for the catalyst due to its large pore size and high surface area, and an efficient three-dimensional interconnectional pathway of pores. Its large nanopores and good porous structure are highly effective in terms of the substrate mass transfer mechanism, and it can withstand coke formation due to its resistance capabilities. Figure 3 shows the nitrogen desorption data. We can deduce that the ash-supported catalyst displayed type IV isotherms and H2 hysteresis loops, which is evident for materials that pose mesoporous and interconnectional pores [1].
Generally, ash-combination catalysts (Ash:MgO 1:1, 1:2, 1:3, and Ash:MgO/ZrO2 1:1:1) retained their surface area while their pore volume decreased. The increase in weight was due to the incorporation of the Mg-metal, which indicates the deposition of the metal substrate within the pores of the supported ash with some silica elements (Table 2). Moreover, the formation of small metal oxide nanoparticles ensures that the pore sizes are retained and avoid decomposition [31,32].

2.4. SEM Analysis for the Catalyst

To understand the surface morphology of the ash-combined catalyst, an SEM analysis was performed to investigate Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 (1:1:1). Figure 4 shows the image displayed by the electron micrograph of the four samples. It was observed that the Ash:MgO/ZrO2 base had a uniform distribution of ZrO2 support incorporated into the ash and Mg metal. Ash:MgO (1:1) has a small ball-like surface with particles of MgO spread around the surface. Ash:MgO (1:2) showed only a few distinct structural destructions, which is potentially due to the preparation method. It modifies itself during co-precipitation. The morphology of Ash:MgO (1:3) was similar to (1:1) but with more of the Mg-metal incorporated onto the surface. The morphology of the Ash:MgO/ZrO2 (1:1:1) catalyst with the co-precipitation treatment was a relatively rough surface with distinct irregular structures. The surface structure of this catalyst was destroyed; during co-precipitation, a new surface structure was formed with Ash, Mg, and Zr.

2.5. Effect of Ash as Catalysts on Ethanol Dehydration

Ash was tested in different combinations for the possible dehydration of ethanol to 1,3-butadiene. This study discusses the conversion of ethanol, yield, and selectivity of 1,3-butadiene as a major product. The by-products were acetaldehyde and ethylene in some cases. The following combinations were analyzed: Ash, Ash:MgO (1:1), Ash:MgO (1:2), Ash:MgO (1:3), and Ash:MgO/ZrO2 (1:1:1). The generation rate of 1,3-butadiene is directly proportional to ethanol’s WHSV [1,33]. Mass transfer increases are effective, resulting from increased space and gas velocity [34].

2.5.1. Effect of WHSV for Ash as Catalyst at Different Reaction Temperatures

Figure 5 shows that ash led to an ethanol conversion of 20% at 400 °C. The ethanol conversion increases as the temperature increases from 250 °C to 400 °C. At a WHSV of 2.5 h−1, the 1,3-butadiene yield was 16% at 400 °C, and at 0.75 h−1, the 1,3-butadiene yield was 10% at 400 °C. The 1,3-butadiene yield was favored at high temperatures when ash was used as a catalyst [35]. When the temperature was 400 °C, the selectivity of 1,3-butadiene was 65% at 2.5 h−1, 61% at 1.25 h−1, 50% at 6.0 h−1,, and 45% at 0.75 h−1,, respectively. In general, the selectivity of 1,3-butadiene increases with increasing temperatures. At 350 °C and 1.25 h−1, the selectivity of acetaldehyde was 3%, while ethylene was 0.9%, respectively. Ash as a catalyst contains different constituents of elements, of which 84% is SiO2 and other trace metals and compounds; thus, some of these elements tend to favor other by-products such as bio-acid or ketones. Overall, it converts ethanol but provides different products at a high yield.

2.5.2. Effect of WHSV for Ash:MgO (1:1) at Different Reaction Temperatures

Figure 6 highlights the use of ash in combination with MgO (1:1). This combination achieved an ethanol conversion of 60% at 350 °C and 2.5 h−1. At a WHSV of 2.5 h−1 and 1.25 h−1, the ethanol conversion rate was 60% and 57%, respectively. At 6.0 h−1 and 0.75 h−1, the ethanol conversion decreased to 40% at 350 °C. However, ethanol conversion reached a static constant in the range of 45–40% at 400 °C.
The presence of MgO supports the catalytic activity and provides stability for the catalytic system. The 33.3% yield of 1,3-butadiene was positive because the ash contained some trace elements. In addition, MgO provided the Lewis basic site for eliminating water from acetaldol and the dehydrogenation of crotonaldehyde. Finally, SiO2 and some metals such as Ca and Na appeared in the ash aid when removing water from crotyl alcohol to produce 1,3-butadiene as the main product. This result helps explain the related mechanism. Taifan et al. proposed the step-by-step mechanism of 1,3-butadiene production from the metal catalyst [36].

2.5.3. Effect of WHSV for Ash:MgO (1:2) at Different Reaction Temperature

Figure 7 shows that ash, combined with MgO at a ratio of 1:2, has an ethanol conversion rate of 79% at 350 °C and 2.5 h−1. The conversion of ethanol increases from 50% to 79% with a rise in temperature from 250 to 350 °C, respectively; however, it drops when the temperature reaches 400 °C (79–65%). At 350 °C, ethanol conversion with WHSV was as follows: 0.75 h−1, 6.0 h−1, 1.25 h−1, and 2.5 h−1 were 57%, 60%, 75.6%, and 79%, respectively.
Moreover, ash, in combination with MgO at a 1:2 ratio, has a higher ethanol conversion rate than 1:1 and 1:3. As suggested by Dahan et al., a balance in terms of size distribution and the creation of the active site for the Lewis acidic and basic reaction was needed for 1,3-butadiene production [37]. The yield and selectivity of 1,3-butadiene were 48% and 87.8%, respectively, at 350 °C and WHSV = 2.5 h−1. When WHSV was reduced from 6.0 h−1 to 1.25 h−1, the yield of 1,3-butadiene increased. Acetaldehyde had a yield of 15%, while ethylene had a yield of 8% at 350 °C. The presence of MgO aided further in crotonaldehyde hydrogenation with Meerwein–Ponndorf–Verley reduction with ethanol and the resulting alcohol was dehydrated to 1,3-butadiene. Since ash is composed of SiO2 and some NaO and CuO, CuO introduces redox-active acidic sites, but poison is the acidic site of the SiO2, which reverts ethylene condensation to 1,3-butadiene production. The presence of NaO aids in the conversion of acetaldehyde, which is converted by CuO redox-sites, to crotyl aldehyde, which is then dehydrated to prevent incomplete ethanol conversion [3,20,38].

2.5.4. Effect of WHSV for Ash:MgO (1:3) at different Reaction Temperature

Figure 8 shows the ethanol conversion, yield, and selectivity of 1,3-butadiene, acetaldehyde, and ethylene using ash + MgO (1:3). At 350 °C and 2.5 h−1, the conversion of ethanol was 65%, but the pattern of ethanol conversion to WHSV was 2.5 h−1 > 1.25 h−1> 6.0 h−1 > 0.75 h−1. The increase in the ethanol conversion pattern in relation to temperature was 250 °C< 300 °C< 350 °C; however, at 400 °C, ethanol conversion gradually decreased to 40%. Nevertheless, the yield of 1,3-butadiene was 25% at 350 °C, compared to Ash:MgO (1:1), which was 33.3%, and Ash:MgO (1:2), which was 48%. The result showed that the proportional ratio of ash to MgO affected ethanol conversion and product yield distribution (1,3-butadiene, acetaldehyde, and ethylene). Lewandowski also considered this idea and stated that MgO was used as a support and provided the basic active sites [39]. SiO2 (ash) was needed in small amounts, aiding in the selectivity of 1,3-butadiene. The presence of SiO2 in small quantities is vital as it aids in the dispersion of the metal element and catalyzes the condensation and dehydration stages in the catalytic reaction. The selectivity of 1,3-butadiene was 83.4% at 350 °C and 2.5 h−1 compared to 87.8% for Ash:MgO (1:2). The selectivity of 1,3-butadiene in relation to WHSV is as follows: 2.5 h−1: 83.4%, 1.25 h−1: 80.3%, 6.0 h−1: 75.6%, and 0.75 h−1: 70%, respectively. For a WHSV of 2.5 h−1, 1.25 h−1, and 6.0 h−1, the selectivity of 1,3-butadiene increases with an increase in temperature; however, at 400 °C, 2.5 h−1, and 1.25 h−1, the selectivity of 1,3-butadiene drops while the selectivity of 1,3-butadiene increases at 6.0 h−1 and 0.75 h−1. The acetaldehyde yield was 25% at 350 °C, while the ethylene yield was 12%.

2.5.5. Effect of WHSV Using Ash:MgO/ZrO2 (1:1:1)

Figure 9 shows the ethanol conversion, yield, and selectivity of 1,3-butadiene using the Ash:MgO-ZrO2 catalyst. At 350 °C, the conversion rate of ethanol was 78%. The conversion of ethanol increased from 67.8% at 250 °C to 78% at 350 °C, then dropped to 70% at 400 °C. This might be due to the coke deposition at high temperatures, which causes the catalyst to be less stable. The conversion pattern of ethanol in relation to WHSV was 2.5 h−1 > 1.25 h−1 > 6.0 h−1 > 0.75 h−1, while the pattern of conversion of ethanol in relation to an increase in temperature was 250 °C < 300 °C < 350 °C.
At 350 °C, the selectivity of 1,3-butadiene was 90.8% at 2.5 h−1. The selectivity of 1,3-butadiene at 2.5 h−1 as temperature increased was 70% (250 °C), 83.2% (300 °C), 90.8% (350 °C), and 80% (400 °C). This activity was in accordance with the studies of Lewandowski et al., which indicate that the Zr addition increases 1,3-butadiene selectivity. Hence, the ZrO2 in Ash:MgO/ZrO2 catalyzed the aldol and dehydrogenation stages in the catalytic ethanol conversion to 1,3-butadiene. ZrO2, in the monoclinic and tetragonal structure, possesses Lewis acidic and basic sites, which interact with the hydrogen of the methyl group of ethanol and could possibly make the creation of H–H realistic. The 1,3-butadiene yield was 70%, the acetaldehyde yield was 6%, and the ethylene yield was 0.9% at 350 °C and 2.5 h−1. Ash provides the catalyst’s redox sites and the Brønsted acidic sites from SiO2, catalyzing the aldol to 1,3-butadiene [40,41,42].

2.6. Effect of Time on Stream on Ethanol Dehydration

We summarized the stability of the catalyst for ash when exposed to 350 °C for 14 h in different combinations. In this section, ash as a parent catalyst was combined in different proportions with MgO and ZrO2. The selectivity of 1,3-butadiene was examined in optimal conditions. Figure 10 shows the performance of ash in different proportions with MgO and ZrO2. At 350 °C and WHSV 2.5 h−1, the conversion of ethanol gradually decreased after 4 h; then, it achieved stability for 10 h. The finding shows that ash, in combination with MgO and ZrO2, has a higher 1,3-butadiene selectivity, and ash combined with MgO in a proportion of 1:2 has a higher ethanol conversion. Ash alone shows an ethanol conversion of 20% for 8 h, with a 1,3-butadiene yield and selectivity of 16% and 65%, respectively. It contains a percentage of SiO2, which provides Brønsted acidic and basic sites for ethanol dehydration. Ash:MgO (1:1) has an ethanol conversion of 60%, with a 1,3-butadiene yield and selectivity of 33.3% and 79.2%, respectively. Ash:MgO (1:3) has an ethanol conversion of 65% and 1,3-butadiene yield and selectivity of 25% and 87.3%, respectively. The Ash:MgO (1:2) catalyst has an ethanol conversion rate of 79% and 1,3-butadiene yield and selectivity of 48% and 88.7%, respectively. The Ash:MgO (1:2) has a better catalytic effect for the 1,3-butadiene yield than 1:1 and 1:3 (1:2 > 1:1 > 1:3). However, in terms of ethanol conversion, the performance follows a different pattern of 1:2 > 1:3 > 1:1. Generally, the MgO catalyst provides an increasing effect for the selectivity of 1,3-butadiene as it aids in the catalyzation of the acetaldol and hydration steps in ethanol dehydration synthesis. For Ash:MgO-ZrO2, at 350 °C, the ethanol conversion was 78%, and 1,3-butadiene yield and selectivity were 70% and 90.7%, respectively.
This specific catalyst generates a mechanism of ethanol dehydration as follows: firstly, ethanol was dehydrogenated to form acetaldehyde; secondly, there was a molecular collision reaction between the two molecules of acetaldehyde which resulted in the formation of acetaldol; thirdly, the molecules then underwent dehydration synthesis to form crotonaldehyde; and a reduction process followed this to generate crotyl alcohol which was further dehydrated to produce 1,3-butadiene. The by-products of catalytic ethanol dehydration were acetaldehyde and ethylene, as their yield and selectivity varied with different proportions of ash, MgO, and ZrO2.

3. Materials and Methods

3.1. Materials

The ash catalyst was obtained from rice straw in our lab. The inorganic compositions of bio ash analyzed by XRF were SiO2 (84.9%), CaO (4.6%), Na2O (2.72.3%), SO3 (2.1%), K2O (1.7%), Al2O3 (0.7%), Fe2O3 (0.4%), and MgO (0.4%). MgO and ZrO2 were purchased from Daiichi Kigeneso Kagaku Kogyo (Tokyo, Japan), ethanol (98%) from Echo Chemical (Miaoli, Taiwan), acetone and ammonium hydroxide (NH4OH) from Sigma Aldrich (St Louis, MI, USA), hydrochloric acid and ammonium phosphate from Sigma (Utah’s Salt Lake, UT, USA), and 1,3-butadiene (10% in nitrogen) and ethylene (10% in nitrogen) from Ming Yang (Taoyuan, Taiwan).

3.2. Catalyst Preparation

The ash combination catalyst (MgO and ZrO2) was prepared in the process of co-precipitation with diluted NH4OH. In total, 3.4 g of MgO, 3.4 g of ash, and 3.4 g of ZrO2 were dissolved separately in deionized water and mixed vigorously. The NH3 solution was added in drops with frequent stirring until complete precipitation occurred at pH (11.0). The solution was then filtered and washed with ice-distilled water. This was performed to free any ammonium nitrate or chloride ions. The residue was dried for 48 h at 95 °C under oxygen in an oven. The sample was later calcined at 700 °C under air. The same preparation procedure was carried out for Ash:MgO (1:1), (1:2), (1:3), and Ash:MgO/ZrO2 (1:1:1).

3.3. Dehydration of the Ethanol in a Fixed Bed Reactor

Ethanol dehydration was carried out using a fixed bed with N2 as the gas carrier, as in our previous study [1]. A gas chromatograph with a flame ionized detector was used (GC-FID; GC 14B, Shimadzu, Kyoto, Japan), which has a column of Porapak-Q-141023J (length, 3 m; diameter: 2 mm; and film, 1 μm; Quadrex, Bethany, CT, USA) under a nitrogen carrier gas (30 mL/min). The chromatograph oven conditions were 60–150 °C with a 10 °C/min ramp rate.
A fixed bed reactor was used for catalyst testing with constant temperature and pressure conditions. In total, 0.4 g of the catalyst sample was placed into a stainless tube which was inserted vertically into the furnace. For an easy flow condition to be achieved, powered silica was used to increase the bed width. The fixed bed reactor induced with 0.4 g of the catalyst sample and ethanol had a flow of 30 cm3/min for N2 as a gas carrier. The analytical process in the determination of 1,3-butadiene used was identical to that reported by Bojang and Wu [1]. WHSV is defined as the ratio of the hourly feed flow of ethanol divided by the catalyst weight in grams [1].

3.4. Catalyst Characterization

The catalyst was characterized using XRD, XPS, SEM, BET, and TGA. The X-ray diffraction pattern was acquired on a D2 diffractometer scanning 2θ from 10° to 90°, and the operation condition was 40 kV and 40 mA using 0.1 g of the catalyst [1]. The surface chemistry and element orbital spin were analyzed with an X-ray photoelectron spectroscopy (XPS). The sample analysis was undertaken with the aid of the 5700C instrument (Perkin Elmer, Akron, OH, USA), with MgKα radiation (1253.6 eV) using 0.1 g of the catalyst. The data fitting of the XPS peak was achieved using Gaussian squares or the Lorentzian peak geometry [1]. The thermal characteristic of the catalyst was analyzed using thermogravimetric tools (TGA) (TA instruments Q50, Milford, MA, USA). This was important to determine the coke deposition on the catalyst. The sample was heated from 25 °C to 800 °C at a ramp rate of 10 °C/min under nitrogen gas flow conditions.
A nitrogen adsorption–desorption isotherm was investigated at −196 °C with ASAP2020 (Micrometrics, Drive Norcross, GA, USA). Before measurement, the sample was degassed in a vacuum at 200 °C for 200 min (ramp rate 10 °C/min−1). The Brunauer–Emmett–Teller method was utilized to calculate the specific surface areas by using adsorption data in a relative pressure range from 0.02 to 0.25. The pore diameters in a size range of 2~50 nm were considered mesoporous, and pore sizes of less than 2 nm were considered micro-porous; pore sizes larger than 50 nm are considered macro-porous. A scanning electron microscope (SEM) (JEOL JSM-5600, Tokyo, Japan) was used to measure the microcosmic structure of the catalytic surface. Before the SEM analysis, part of the catalyst was compressed and placed into the sample processor while the turbo pump system decompressed the start pressure until it reached 2 × 10–6 KPa from 1 atm. Then, the gate value between the sample processor and the vacuum room increased.

4. Conclusions

Ethanol dehydration was conducted using ash as a catalyst to produce 1,3-butadiene. When ash combines with MgO (1:2), it achieves an ethanol conversion of 79% and a 1,3-butadiene yield of 48.3% at 350 °C and a WHSV of 2.5 h−1. Importantly, the presence of ZrO2 in the Ash:MgO catalytic system leads to an ethanol conversion of 78% and a 1,3-butadiene yield of 70%; the selectivity of 1,3-butadiene was 96.7% at 350 °C. Based on this result, a suitable weight ratio of ash to MgO was used to obtain a high yield of 1,3 butadiene. ZrO2 was added to the ash catalyst to increase the thermal stability of the catalyst.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal13020258/s1, Figure S1: XRD for blank ash and with different combination.

Author Contributions

Conceptualization, H.S.W.; investigation and research, A.A.B.; writing—original draft preparation, A.A.B.; writing—review and editing, H.S.W.; supervision, H.S.W. All authors have read and agreed to the published version of the manuscript.

Funding

The Ministry of Science and Technology of Taiwan: MOST 109-2221-E-155-009.

Data Availability Statement

No applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 13 00258 g001 550
Figure 1. XRD pattern of Ash:MgO (1:1), (1:2), (1:3) and Ash:MgO/ZrO2 (1:1:1).
Figure 1. XRD pattern of Ash:MgO (1:1), (1:2), (1:3) and Ash:MgO/ZrO2 (1:1:1).
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Catalysts 13 00258 g002 550
Figure 2. XPS profile for Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 (1:1:1).
Figure 2. XPS profile for Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 (1:1:1).
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Catalysts 13 00258 g003 550
Figure 3. N2 absorption and desorption, isothermal and pore size distribution plot (inserted) of Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 (1:1:1).
Figure 3. N2 absorption and desorption, isothermal and pore size distribution plot (inserted) of Ash:MgO (1:1, 1:2, 1:3) and Ash:MgO/ZrO2 (1:1:1).
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Catalysts 13 00258 g004 550
Figure 4. SEM profile of (A) Ash:MgO (1:1), (B) Ash:MgO (1:2), (C) Ash:MgO (1:3), and (D) Ash:MgO/ZrO2 (1:1:1).
Figure 4. SEM profile of (A) Ash:MgO (1:1), (B) Ash:MgO (1:2), (C) Ash:MgO (1:3), and (D) Ash:MgO/ZrO2 (1:1:1).
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Catalysts 13 00258 g005 550
Figure 5. Plot of the ash catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Figure 5. Plot of the ash catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Catalysts 13 00258 g005
Catalysts 13 00258 g006 550
Figure 6. Plot of the Ash:MgO (1:1) catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Figure 6. Plot of the Ash:MgO (1:1) catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Catalysts 13 00258 g006
Catalysts 13 00258 g007 550
Figure 7. Plot of the Ash:MgO (1:2) catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Figure 7. Plot of the Ash:MgO (1:2) catalyst (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Catalysts 13 00258 g007
Catalysts 13 00258 g008 550
Figure 8. Plot of (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV using Ash:MgO (1:3) catalyst. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Figure 8. Plot of (a) ethanol conversion, (b) yield of 1,3-butaiene (c) acetaldehyde yield (d) ethylene yield (e) 1,3-butadiene selectivity and (f) acetaldehyde selectivity at different reaction temperatures and WHSV using Ash:MgO (1:3) catalyst. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Catalysts 13 00258 g008
Catalysts 13 00258 g009 550
Figure 9. Plot of the Ash:MgO/ZrO2 (1:1:1) catalyst ethanol conversion (a), yield (b) and selectivity (e) of 1,3-butadiene, yield (c) and selectively (f) of acetaldehyde, and ethylene yield (d) at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Figure 9. Plot of the Ash:MgO/ZrO2 (1:1:1) catalyst ethanol conversion (a), yield (b) and selectivity (e) of 1,3-butadiene, yield (c) and selectively (f) of acetaldehyde, and ethylene yield (d) at different reaction temperatures and WHSV. Catalyst: 0.4 g, WHSV = 0.75–6.0 h−1, N2: 30 mL/min.
Catalysts 13 00258 g009
Catalysts 13 00258 g010 550
Figure 10. Conversion of ethanol for the (a), yield of 1,3-butadiene (b), selectivity of 1,3-butadiene (c), yield of acetaldehyde (d), yield of ethylene (e), and selectivity of acetaldehyde (f) with time on streams. WHSV: 2.5 h−1, 0.4 g of catalyst, N2 = 30 mL/min, Temp: 350 °C.
Figure 10. Conversion of ethanol for the (a), yield of 1,3-butadiene (b), selectivity of 1,3-butadiene (c), yield of acetaldehyde (d), yield of ethylene (e), and selectivity of acetaldehyde (f) with time on streams. WHSV: 2.5 h−1, 0.4 g of catalyst, N2 = 30 mL/min, Temp: 350 °C.
Catalysts 13 00258 g010
Table
Table 1. Elemental weight percentage analysis using XPS.
Table 1. Elemental weight percentage analysis using XPS.
CatalystO 1s
(%)		C 1s
(%)		Zr 3d
(%)		Si 2p
(%)		Mg 1s
(%)		Na 1s
(%)
Ash:MgO (1:1)60.87.3-28.71.01.2
Ash:MgO (1:2)58.79.9-25.33.82.5
Ash:MgO (1:3)62.65.8-26.34.40.9
Ash:MgO/ZrO2 (1:1:1)44.414.010.320.211.1-
Table
Table 2. Catalyst size analyzed according to BET surface area and pore volume.
Table 2. Catalyst size analyzed according to BET surface area and pore volume.
CatalystBET Surface Area (m2/g)Pore Volume (cm3/g) α
Ash:MgO (1:1)27.40.2432
Ash:MgO (1:2)28.50.2763
Ash:MgO (1:3)29.30.3419
Ash:MgO/ZrO2 (1:1:1)44.30.3927
α Estimated at a relative pressure of P/P0 = 0.98.
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Bojang, A.A.; Wu, H.S. 1,3-Butadiene Production Using Ash-Based Catalyst. Catalysts 2023, 13, 258. https://doi.org/10.3390/catal13020258

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Bojang AA, Wu HS. 1,3-Butadiene Production Using Ash-Based Catalyst. Catalysts. 2023; 13(2):258. https://doi.org/10.3390/catal13020258

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Bojang, Adama A., and Ho Shing Wu. 2023. "1,3-Butadiene Production Using Ash-Based Catalyst" Catalysts 13, no. 2: 258. https://doi.org/10.3390/catal13020258

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